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Old March 23rd 07, 12:44 PM posted to rec.radio.amateur.antenna
Keith Dysart Keith Dysart is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 124
Default Revisiting the Power Explanation

On Mar 22, 12:20 am, Cecil Moore wrote:

This is a lot like the 1/2WL W7EL example in his food for
thought articles. The generator is *NOT* matched to the line
as it sees an open circuit and cannot continue to stuff 50
watts into the open circuit. The generator is as mismatched
as it can possibly be. The reflected wave also sees that open
circuit and is 100% reflected. Since the generator is not
delivering any power and there is a forward power and a
reflected power, the reflected power is supplying the
forward power. Anything else violates the conservation
of energy principle.


I suggest that you have quite mixed up your impedances here
thus rendering all further analysis invalid.

At any point in the system there are 4 impedances.

There is the characteristic impedance looking left and the
characteristic impedance looking right. For systems in
sinusoidal steady-state, there is also the effective impedance
looking left and the effective impedance looking right.

The characteristic impedance is dependant only the elements of
the system. It does not depend on the length of the line or
the frequency of excitation. At changes in the characteristic
impedance, reflections occur. This impedance can be used for
transient as well as steady-state analysis of a system.

The effective impedance is dependant on the characteristic
impedances of the components of the system, as well as line
length and excitation frequency. It can only be used for
steady-state analysis. It does not cause reflections.

Until these impedances are kept straight in discussions, there
is no hope for correctness.

....Keith